In my opinion, the more inputs you get on an interface the more you could do without your mixer.
The mixer could still be useful if, for example, your interface only had two inputs and you wanted to record a multi-miced drumkit. You could get a sub-mix to a stereo out from your mixer and record that into a stereo pair on your interface and onto a stereo track in Cubase.
Really, there is nothing stopping you from running everything through your mixer before your interface. It’s all personal preference. You’ll have to figure out what works for you.
I started out with a mixer/simple interface setup and now have a multiple input interface and have ditched the mixer from the DAW.